1. Field of the Invention
The present invention relates to a printing apparatus and a recovering method therefor.
2. Description of the Related Art
Printing apparatuses that print information such as text and images on printing media have been known. Examples of a printing method adopted in such printing apparatuses include an inkjet printing method that uses ink for printing. A printing apparatus using such an inkjet printing method (hereinafter, referred to as an inkjet printing apparatus or a printing apparatus) is provided with an ink tank for storing ink. As an example of an ink tank, a combined type ink tank is known that has a negative pressure generation chamber, an ink storage chamber that is communicated only with the negative pressure generation chamber, and a supply orifice for supplying ink from the negative pressure generation chamber (Japanese Patent Laid-Open No. 06-040043).
Here, such a printing apparatus is configured to perform various recovery operations to recover poor ink discharge. Examples of a recovery operation include a refreshing operation performed in order to recover printing quality. A user gives an instruction to execute this recovery operation. Also, the above examples include a tank replacement recovery operation performed in order to remove air bubbles taken in from a joint portion between an ink tank and a printhead when the ink tank is attached/detached. This recovery operation is automatically performed immediately after tank replacement, or before the start of the first printing processing after tank replacement.
Examples of a recovery unit include a capping mechanism to cap a discharge orifice surface of the printhead. With the recovery unit, ink is compulsorily discharged from the discharge orifice using a suction unit (such as a suction pump) in conjunction with the discharge orifice surface being capped by the capping mechanism. Further, technology for changing suction control according to the environmental temperature of a printing apparatus is known. For example, if the environmental temperature is high, the solubility of air will fall. In this case, since bubbles, which cause poor discharge, tend to remain in a nozzle, “strong suction (for example, suction for which a suction amount per unit time is comparatively large)” is suitable. On the other hand, if the environmental temperature is low, “weak suction (for example, suction for which a suction amount per unit time is comparatively small)” is performed, and thus wasteful ink consumption can be suppressed when removing bubbles. As known techniques for selecting a recovery operation by detecting the environmental temperature, there is a system in which a temperature sensor is provided on the apparatus main body side (Japanese Patent Laid-Open No. 08-267786, Japanese Patent Laid-Open No. 09-290517), and a system in which a temperature sensor is provided on the ink tank side that is to be replaced (Japanese Patent Laid-Open No. 2007-223160). In consideration of the fact that ink tanks are consumables, the system in which a temperature sensor is provided on the apparatus main body side is more advantageous in terms of cost. In the description below, a technique for changing suction control according to the environmental temperature may also be simply referred to as “environmental suction”.
With the combined type ink tank, if a large amount of printing is performed in a short time, air corresponding to the amount of ink supply enters a liquid storage room, and thus the air-liquid interface lowers, and even reaches the ink supply orifice. It is known that this causes the occurrence of so-called “running out of ink”, which is the state of no ink being supplied from an ink tank (Japanese Patent Laid-Open No. 2005-349730).
In regard to this, from the study done by the inventors of the present invention, it was found that the above “running out of ink” may occur not only when a large amount of printing is performed in a short time, but also when a suction recovery operation is performed. One of the causes for this is that an air path is formed in an absorbing member by rapidly sucking ink whose flow resistance has increased due to increased viscosity. In order to avoid this, in the state where the ink viscosity has increased due to a low ink temperature, it is necessary to discharge nozzle bubbles by performing “weak suction”. With the apparatus that performs environmental suction described above, the problem of the above running out of ink does not occur since “weak suction” is implemented if it is detected that the environmental temperature is low. Further, in the state where the environmental temperature is high, and the ink temperature is also high, since the viscosity of ink is not very high, even if “strong suction” is implemented, running out of ink does not occur.
However, even though if the detected environmental temperature is high, if the actual ink temperature is low, “strong suction” will be implemented with respect to the ink whose viscosity has increased, and thus there is the possibility that ink may run out. For example, suppose that some of the ink tanks in a printing apparatus being used in an approximately 25° C. environment are replaced with ink tanks that have been saved in an approximately 5° C. environment. In this case, although the printing apparatus detects that the ink temperature is high based on the environmental temperature, the actual ink temperature is low.
Although the temperature of the replaced ink tanks will gradually conform to the temperature of the environment (25° C.) where they are placed as time elapses, if a suction operation is executed as part of a tank replacement recovery operation immediately after the replacement, it is detected that the environmental temperature is 25° C. even though the ink temperature has not reached 25° C., and thus a recovery operation using “strong suction” will be performed. At this time, a strong negative pressure will be applied on the low-temperature ink tanks, and thus there is the risk of the occurrence of running out of ink.